Simplified vs extended in vitro methods for the evaluation of bioaccessibility of metals and metalloids present in urban recreational soils

Urban soils may contain different metals and metalloids and they can enter the human body by direct inhalation, ingestion or dermic absorption. According to USEPA, 200 mg·day⁻¹ is the average daily ingested dose of soil for children aged from 1 to 12 years of age. In vitro bioaccessibility tests which are based on human physiology, have been used for the determination of the element fraction in soils that can be absorbed by human digestion. A total of 26 urban soils were collected in recreational areas from San Sebastian to evaluate the bioaccessibility of metals and metalloids (Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Cd and Pb) by SBET (Simplified Bioaccessibility Extraction Test) and RIVM (Dutch National Institute for Public Health and Environment) in vitro methodologies. SBET simulates the gastric conditions, while RIVM simulates mouth, gastric and intestinal conditions. ICP-MS was used for the simultaneous determination of the elements. Cd showed the highest percentage of bioaccessibility by both methods and Fe, Al and Cr resulted the least bioaccessible elements. Pb and Zn showed different results in each method. HQ (Hazard Quotient), HI (Hazard Index) and CR (Carcinogenic Risk) values obtained were higher with SBET methodology. According to HI (considering 10 metal(loid)s), non-carcinogenic effects may occur to children with the ingestion of three of the studied children’s parks. Regarding CR index, all the studied soils were within the tolerable carcinogenic risk (considering Cr, As and Pb) for children, and the risk was sometimes negligible for adults. Considering the experimental difficulties related to RIVM, SBET method may be used for a simple and conservative first approach of the bioaccessibility of metals and metalloids accumulated in soil samples.